Am79C973/Am79C975
153
P R E L I M I N A R Y
VER is read only. Write opera-
tions are ignored.
27-12 PARTID
Part number. The 16-bit code for
the Am79C973 controller is
0010 0110 0010 0101 (2625h)
and the code for the Am79C975
is 0010 0110 0010 0111 (2627h).
This register is exactly the same
as the Device ID register in the
JTAG description. However, this
part number is different from that
stored in the Device ID register in
the PCI configuration space.
Read accessible only when either
the STOP or the SPND bit is set.
PARTID is read only. Write oper-
ations are ignored.
11-1
MANFID
Manufacturer ID. The 11-bit man-
ufacturer code for AMD is
00000000001b. This code is per
the JEDEC Publication 106-A.
Note that this code is not the
same as the Vendor ID in the PCI
configuration space.
Read accessible only when either
the STOP or the SPND bit is set.
VER is read only. MANFID is
read only. Write operations are
ignored.
0
ONE
Always a logic 1.
Read accessible only when either
the STOP or the SPND bit is set.
VER is read only. ONE is read
only. Write operations are ig-
nored.
CSR89: Chip ID Register Upper
Bit
Name
Description
31-16 RES
Reserved locations. Read as un-
defined.
15-12 VER
Version. This 4-bit pattern is
silicon-revision dependent.
Read accessible only when either
the STOP or the SPND bit is set.
VER is read only. VER is read
only. Write operations are ig-
nored.
11-0
PARTIDU
Upper 12 bits of the Am79C973/
Am79C975 controller part num-
ber, i.e., 0010 0110 0010b
(262h).
Read accessible only when either
the STOP or the SPND bit is set.
VER is read only. PARTIDU is
read only. Write operations are
ignored.
CSR92: Ring Length Conversion
Bit
Name
Description
31-16 RES
Reserved locations. Written as
zeros and read as undefined.
15-0
RCON
Ring Length Conversion Regis-
ter. This register performs a ring
length conversion from an encod-
ed value as found in the initializa-
tion block to a two
’
s complement
value used for internal counting.
By writing bits 15-12 with an en-
coded ring length, a two
’
s com-
plemented value is read. The
RCON register is undefined until
written.
Read/Write accessible only when
either the STOP or the SPND bit
is set. These bits are unaffected
by H_RESET, S_RESET, or
STOP.
CSR100: Bus Timeout
Bit
Name
Description
31-16 RES
Reserved locations. Written as
zeros and read as undefined.
15-0
MERRTO
This register contains the value of
the longest allowable bus latency
(interval between assertion of
REQ and assertion of GNT) that a
system may insert into an
Am79C973/Am79C975 controller
master transfer. If this value of
bus latency is exceeded, then a
MERR will be indicated in CSR0,
bit 11, and an interrupt may be
generated, depending upon the
Device
CSR88
Am79C973
5003h
Am79C975
7003h